1. Field of the Invention
This invention relates to drip or trickle irrigation, and more particularly, to a new and improved drip irrigation hose which includes a primary channel or conduit for receiving a supply of liquid, and a secondary, regulatory conduit characterized by a strip or plate of material provided between the lapped edges of the primary conduit and having multiple fluid flow paths inscribed in the plate and extending in a repetitive pattern from the high pressure interior of the primary conduit through paths formed by adjacent segments of the plate, and exiting to the surroundings at the low pressure discharge side of the plate. In a preferred embodiment, each flow path in the regulatory secondary conduit is small and zigzag in nature and serves to reduce the water or liquid pressure from the interior of the primary conduit to the point of discharge of the liquid from the regulatory secondary conduit to the atmosphere.
A primary problem which must be solved in the design of a drip or trickle irrigation hose is the provision of a regulated, uniform drip or trickle discharge from a supply conduit containing irrigation liquid under pressure. The problem becomes more acute as the pressure in the supply conduit varys along the length of the conduit. The problem cannot be adequately solved merely by providing a simple series of spaced apertures in the supply conduit, since in general, the fluid pressure at the point of entry of the liquid into the supply conduit is higher than the pressure in the conduit farthest away from the point of entry. This decreasing pressure along the length of the conduit resulting from discharge of water or liquid through the spaced apertures and the pressure drop due to friction normally associated with liquid flow through the conduit, tends to result in a larger rate of discharge of water or fluid from apertures near the point of entry of the water into the conduit and a lesser discharge rate from apertures at the opposite end of the conduit.
2. Description of the Prior Art
Various emitter systems have been proposed by those skilled in the art to effect a uniform rate of fluid or liquid discharge along the length of the drip irrigation hose. Some hoses utilize very small apertures in the wall of the supply conduit in order to achieve the desired flow rate from the conduit. However, this system suffers from the disadvantage of requiring the use of a relatively high pressure fluid source and a high discharge rate. Also, since the apertures are so small, sand and other materials in the irrigating liquid easily easily block them Additionally, use of only short lengths of the drip irrigation hose are possible before the variation in pressure (and, therefore discharge rate) between apertures is too great. Other hose designs allowing the use of larger apertures which are less subject to clogging and permitting longer lengths of run while still providing a uniform discharge flow of satisfactory proportions have taken the form of providing emitters with a complex of orifices and long path tortuous and non-tortuous passages from the point of high pressure to the point of discharge.
These more complex designs require precise and relatively small discharge apertures. Those using relatively long flow paths to reduce the pressure at the emitter discharge frequently provides laminar flow of liquids or fluids through these paths, with a resulting high tendancy to clogging and high sensitivity to pressure variation in the primary conduit or supply chamber. Thus, more complex, tortuous paths are sometimes used to provide a method of facilitating turbulent flow of liquid from the high pressure zone to the point of discharge, thereby allowing a relatively large flow path and reducing the sensitivity of the discharge flow to primary conduit water pressure fluctuations.
Among the attempts to solve the problem of providing a satisfactory drip or trickle irrigation hose is the drip level irrigation apparatus disclosed in U.S. Pat. No. 4,215,822, to R. Mehoudar. This patent defines an emitter unit having a wall characterized by an elongated flow path; an inlet and outlet for the unit; a connector for coupling the unit to an irrigation conduit; and two sets of oppositely-directed members projecting into the flow path to provide a tortuous path for reducing the pressure of the liquid fluid flowing through the flow path. Another patent disclosing a "One-Piece Drip Irrigation Device", is U.S. Pat. No. 3,873,030, to J. S. Barragan, which teaches the use of an irrigation device for attachment to the perforated wall of an irrigation liquid supply pipe, the device including a casing having side and bottom walls and a flange extending outwardly from the edges of an open casing wall. The flange further includes an enclosed housing with multiple, alternate walls which form a passage provided with multiple obstacles to the liquid, and including in one end, a perforation for liquid exit at a reduced pressure. Similiar devices are disclosed in U.S. Pat. No. 3,896,999 and 3,870,236, to J. S. Barragan. U.S. Pat. No. 3,753,527 to L. D. Galbraith, et al, also discloses multiple drip units or irrigators which are attached to a plastic hose, each irrigator having a relatively large metering orifice and a vortex chamber upstream of the metering orifice and designed to swirl the water ahead of the orifice giving the orifice the flow-determining characteristics of a relatively small orifice. The vortex chamber also serves to increase the velocity of the water at the orifice, providing a scouring action at the orifice which works to prevent algae build-up. Other patents designed to achieve a desirable pressure drop between the high pressure supply water and the emitter discharge are U.S. Pat. No. 3,667,685 to Isaac Rinkewich, U.S. Pat. No. 28,095, to R. D. Chaplin and U.S. Pat. No. 4,022,384 to W. I. Hoyle, et al.
One of the problems associated with conventional drip irrigation hose design is the difficulty of manufacturing a uniform product. The requirement to form a precise, complex design frequently leads to a high expense of manufacture, resulting in a high cost to the user.
Accordingly, it is an object of this invention to provide a drip irrigation hose having both a primary and a secondary flow chamber which promote a multiple emitter discharge trickle or drip which is relatively insensitive to pressure variations in the primary feed water stream.
Another object of this invention is to provide a drip irrigation hose which is characterized by a primary channel or chamber for receiving a supply of water or liquid and a secondary, regulatory conduit shaped from a length of material fitted to the primary chamber and characterized by a repetitive pattern of inlet openings from the primary chamber flow paths and discharge orifices or apertures, which flow paths are sized and shaped to facilitate regulated, uniform drip flow of the pressurized liquid inside the primary chamber through the regulatory conduit to the point of discharge.
Another object of the invention is to provide a drip irrigation hose, the primary conduit of which is shaped from a length of film or sheet of resilient material which is lapped at the edges, and a secondary, regulatory conduit characterized by a plate of resilient material coextensive with the primary conduit and having a repetitive flow path pattern therein, and positioned between the lapped edges of the primary conduit with entry ports in spaced relationship along one edge of the secondary conduit or in the lapped edge of the primary conduit and projecting inside the primary conduit and discharge ports or apertures provided in spaced relationship along the opposite edge of the secondary conduit or in the lapped edge of the primary conduit and projecting outside of the primary conduit to direct the flow of liquid from the primary conduit, through the secondary conduit in regulated drip or trickle flow, uniformly along the length of the hose.
Still another object of the invention is to provide a new and improved drip irrigation hose which is characterized by a primary conduit shaped from a length of resilient sheeting having lapped edges to exhibit an essentially round cross section when in use; a regulatory, secondary conduit formed from an elongated, resilient strip or plate of selected thickness laminated between the lapped edges of the primary conduit film and running essentially the entire length of the primary conduit; and a flow path pattern of desired length and configuration included in the secondary conduit to provide a path for the flow of liquid or fluid from the high pressure primary conduit to a low pressure emission point from the secondary conduit, the secondary conduit plate flow paths preferably formed by stamping, cutting or otherwise inscribing the desired flow path pattern into the secondary conduit strip, separating and orienting the segments and securing the segments between the lapped edges of the primary conduit.